Influence of altitude on growth and height-diameter ratio of tree species in mixed forests of Julian Alps

V mešanih gorskih gozdovih na območju južnih Bohinjskih gora smo izvedli raziskavo vpliva nadmorske višine na rast in dimenzijsko razmerje štirih drevesnih vrst. V prvem delu smo s podatki s stalnih vzorčnih ploskev Zavoda za gozdove Slovenije preučili vpliv nadmorske višine na debelinsko rast dreves. Preučeni povprečni 10-letni debelinski prirastek analiziranih drevesnih vrst je z nadmorsko višino praviloma padal. Smreka in gorski javor sta največje debelinske prirastke dosegala v pasu 500-699 metrov nadmorske višine, medtem ko sta jih bukev in jelka v pasu 700-899 metrov. Drugi del raziskave je predstavljala analiza dimenzijskega razmerja, ki smo jo opravili na podlagi lastnih meritev 233 dreves. Ne moremo nedvoumno trditi, da dimenzijsko razmerje pada z naraščajočo nadmorsko višino, saj povprečne vrednosti niso jasno nakazovale tega trenda. Poleg nadmorske višine nanj vpliva predvsem enomernost sestojev, ki dimenzijsko razmerje dreves povečuje, kar z vidika stabilnosti in dovzetnosti za poškodbe ni pozitivno.In mixed mountain forests in the southern Bohinj Mountains, we performed an analysis of the influence of altitude on growth and height-diameter ratio of four main tree species. In the first part, we studied the influence of altitude on the diameter increment of trees using data from permanent samplings plots of the Slovenia Forest Service. The studied average 10-year diameter increment of the analyzed tree species generally decreased with altitude. Norway spruce and sycamore maple reached the largest diameter increments within 500-699 m a. s. l., while European bech and silver fir within 700-899 m altitudinal belt. Secondly, we studied the height-diameter ratio of trees of the main tree species on the basis of the measurements of 233 trees. Based on results, we can not unequivocally claim that the height-diameter ratio decrases with increasing altitude, although such pattern is indicated. Besides altitude, it is affected also by the evenageness of forests, which increases the height-diameter ratio of the trees, making them less stable and more susceptible to damage